Heavy Duty Trucking

SEP 2014

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58 HDT • SEPTEMBER 2014 www.truckinginfo.com
back, the quietness is almost eerie. I couldn't hear it idle,
and its working growl faded away as road speed increased.
Cummins Westport G engines are spark-ignited; a diesel's
compression ignition is more efficient, but produces that
characteristic pounding sound. At highway speeds the
chassis produced some muted mechanical whirring and
tire whine, as well as the slight sound of air rushing past
the mirrors and the cab's front corners. The ride was
smooth, even with a stiff front suspension and the blocky
445-series tires.
Acceleration was brisk as I departed and headed for
nearby Wisconsin 26, a wide two-laner, and turned south,
immediately encountering some memories. As a TV
newsman many years before, I sometimes barreled north
on this highway in a company car at up to 100 mph to
get news film to the station in Green Bay in time for the
6 o'clock broadcast. This day I cruised at 55 to 65 mph,
where the Cummins spun at 1,600 to 1,800 rpm — not
wound out, but far faster than today's low-revving diesels
in road tractors.
This was the highest-rated ISX12 G, and with 400
horses, it had plenty of go-power. If it was consuming fuel
at a fair rate, so what? Natural gas is much cheaper than
diesel, so savings will help pay off the premium price for
the natural gas fuel system.
I turned right on a county road and followed it west
and north a ways. I stopped and backed into a deserted
intersection to reverse course and return the way I came.
Maneuvering was easy and the view out the cab's windows
and through its mirrors was fine, so I never used this
test drive
Truck:
Oshkosh S-series front-discharge, rear-engine, center-cab
mixer chassis, tare 33,950 lbs., GVW 80,000 lbs.
Engine:
Cummins Westport ISX12 G, 11.9 liters (726.2 cu. in.), 400
hp @ 1,800 rpm (2,100 governed), 1,450 lb-ft. @ 1,200
rpm
Transmission:
Allison 4500 RDS (Rugged Duty Series) full automatic,
6-speed double-overdrive
Front axle: 23,000-lb. Oshkosh 23K w/ 5.63 final-drive
ratio and Sheppard XD 120 integrated hydraulic power
steering, on taperleafs
Transfer case:
Oshkosh 21000 2-speed
Lift axle:
25,000-lb. Watson & Chalin AL-2200 non-steering
Tandem axles: 46,000-lb. Meritor RT-46-160 on 46,000-lb.
w/ 5.63 ratio, on Hendrickson Primaax air-ride
Wheelbase:
196 inches
Tires & wheels:
445/65R22.5 Michelin X2L, on 22.5x13-in. Alcoa aluminum
discs
Brakes:
16.5x7-in. S-cam at all wheels
Fuel tanks:
Two 37.5-diesel-gallon-equivalent (75-DGE total) Type 4
CNG (polymer core w/ carbon fiber wrap)
Body:
11-yd. McNeilus forward-facing drum w/ ZF P7300 trans-
mission and Eaton hydraulics
SPECIFICATIONS
The rear-mounted Cummins Westport ISX12 G can't be
heard by the driver at highway speeds. Its gas is stored
in twin vertical Type 4 CNG tanks just ahead. These
replace four horizontal tanks previously used, saving
about 500 pounds and allowing easier access to the
engine. Filler's on the left side.
truck's rear-view camera with its mini TV screen above
the windshield.
I meandered along other roads and onto city streets, and
at one point did a couple of circles on a gravel parking lot.
The wide tires limit wheel cut and make the turning circle
a bit big, but it seemed to corner better than a conven-
tional with a forward-set steer axle and wide tires. With
Sheppard power steering, the truck didn't require much
effort to turn, even while crawling.
Upon my return, I parked it in front of the building.
Recent rain had muddied a section of the back lot, where a
line of new mixer and military trucks awaited transport to
customers. I was tempted to jump back into the S and put
its front-driving axle and lockable differentials on the rear
tandem to a test, but didn't have the heart to get the shiny
white rig dirty. Besides, I've seen them move through mud
and know they're up to it. That's part of what makes this a
seriously mobile and productive truck. n